Pressure-dependent effect of shock waves on rat brain: induction of neuronal apoptosis mediated by a caspase-dependent pathway.

OBJECT: Shock waves have been experimentally applied to various neurosurgical treatments including fragmentation of cerebral emboli, perforation of cyst walls or tissue, and delivery of drugs into cells. Nevertheless, the application of shock waves to clinical neurosurgery remains challenging because the threshold for shock wave-induced brain injury has not been determined. The authors investigated the pressure-dependent effect of shock waves on histological changes of rat brain, focusing especially on apoptosis. METHODS: Adult male rats were exposed to a single shot of shock waves (produced by silver azide explosion) at overpressures of 1 or 10 MPa after craniotomy. Histological changes were evaluated sequentially by H & E staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL). The expression of active caspase-3 and the effect of the nonselective caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK) were examined to evaluate the contribution of a caspase-dependent pathway to shock wave-induced brain injury. High-overpressure (> 10 MPa) shock wave exposure resulted in contusional hemorrhage associated with a significant increase in TUNEL-positive neurons exhibiting chromatin condensation, nuclear segmentation, and apoptotic bodies. The maximum increase was seen at 24 hours after shock wave application. Low-overpressure (1 MPa) shock wave exposure resulted in spindle-shaped changes in neurons and elongation of nuclei without marked neuronal injury. The administration of Z-VAD-FMK significantly reduced the number of TUNEL-positive cells observed 24 hours after high-overpressure shock wave exposure (p < 0.01). A significant increase in the cytosolic expression of active caspase-3 was evident 24 hours after high-overpressure shock wave application; this increase was prevented by Z-VAD-FMK administration. Double immunofluorescence staining showed that TUNEL-positive cells were exclusively neurons. CONCLUSIONS: The threshold for shock wave-induced brain injury is speculated to be under 1 MPa, a level that is lower than the threshold for other organs. High-overpressure shock wave exposure results in brain injury, including neuronal apoptosis mediated by a caspase-dependent pathway. This is the first report in which the pressure-dependent effect of shock wave on the histological characteristics of brain tissue is demonstrated.

[Intraoperative brain surface blood flow monitoring using IRIS V thermographic imaging system in patients with Moyamoya disease].

Surgical revascularization for moyamoya disease prevents cerebral ischemic attacks by improving CBF. But little is known about the changes of intraoperative cerebral hemodynamics and its effect on postoperative neurological status including symptomatic cerebral hyperperfusion. To address this issue, we applied a novel infrared camera system (IRIS-V thermographic system) for real-time, visual monitoring of surface CBF during surgery in patients with moyamoya disease. Seven patients (8 sides, male:female= 3:4, 7-62 years old) with moyamoya disease were included in the study. After STA-MCA anastomosis, STA were occluded transiently and recanalized, and whole sequence was recorded by IRIS-V system. Correlation between clinical, radiological findings and infrared imaging were investigated. Patency of bypass was confirmed by this camera during surgery in all cases. The intraoperative imaging patterns were divided into two groups. Group A: Change of brain surface color (++) (3 cases). Group B: Change of brain surface color (-) (4 cases). Transient symptomatic hyperperfusion occurred in all patients in Group A, whereas all patients in Group B showed non-symptomatic transient focal hyperperfusion on SPECT. No patient suffered permanent neurological deterioration compared to preoperative status. Characteristic pattern of the intraoperative cerebral hemodynamics as delineated by IRIS-V could be the optimal predictor for postoperative transient symptomatic hyperperfusion after direct bypass in patients with moyamoya disease.

Pulsed holmium:yttrium-aluminum-garnet laser-induced liquid jet as a novel dissection device in neuroendoscopic surgery.

OBJECT: A pressure-driven continuous jet of water has been reported to be a feasible tool for neuroendoscopic dissection owing to its superiority at selective tissue dissection in the absence of thermal effects. With respect to a safe, accurate dissection, however, continuous water flow may not be suitable for intraventricular use. The authors performed experiments aimed at solving problems associated with continuous flow by using a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ). They present this candidate neuroendoscopic LILJ dissection system, having examined its mechanical characteristics and evaluated its controllability both in a tissue phantom and in a rabbit cadaveric ventricle wall. METHODS: The LILJ generator was incorporated into the tip of a No. 4 French catheter so that the LILJ could be delivered via a neuroendoscope. Briefly, the LILJ was generated by irradiating an internally supplied column of physiological saline with a pulsed Ho:YAG laser (pulse duration time 350 microsec; laser energy 250-700 mJ/pulse) within a No. 4 French catheter (internal diameter 1 mm) and ejecting it from a metal nozzle (internal diameter 100 microm). The Ho:YAG laser energy pulses were conveyed by an optical fiber (core diameter 400 microm) at 3 Hz, whereas physiological saline (4 degrees C) was supplied at a rate of 40 ml/hour. The mechanical characteristics of the pulsed LILJ were investigated using high-speed photography and pressure measurements; thermal effects and controllability were analyzed using an artificial tissue model (10% gelatin of 1 mm thickness). Finally, the ventricle wall of a rabbit cadaver was dissected using the LILJ. Jet pressure increased in accordance with laser energy from 0.1 to 2 bar; this translated into a penetration depth of 0.08 to 0.9 mm per shot in the ventricle wall of the rabbit cadaver. The gelatin phantom could be cut into the desired shape without significant thermal effects and in the intended manner, with a good surgical view. CONCLUSIONS: The present results show that the pulsed LILJ has the potential to become a safe and reliable dissecting method for endoscopic procedures.

Experimental application of pulsed Ho:YAG laser-induced liquid jet as a novel rigid neuroendoscopic dissection device.

BACKGROUND AND OBJECTIVES: Although water jet technology has been considered as a feasible neuroendoscopic dissection methodology because of its ability to perform selective tissue dissection without thermal damage, problems associated with continuous use of water and the ensuing fountain-effect-with catapulting of the tissue-could make water jets unsuitable for endoscopic use, in terms of safety and ease of handling. Therefore, the authors experimented with minimization of water usage during the application of a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ), while assuring the dissection quality and the controllability of a conventional water jet dissection device. We have developed the LILJ generator for use as a rigid neuroendoscope, discerned its mechanical behavior, and evaluated its dissection ability using the cadaveric rabbit ventricular wall. STUDY DESIGN/MATERIALS AND METHODS: The LILJ generator is incorporated into the tip of a stainless steel tube (length: 22 cm; internal diameter: 1.0 mm; external diameter: 1.4 mm), so that the device can be inserted into a commercial, rigid neuroendoscope. Briefly, the LILJ is generated by irradiating an internally supplied water column within the stainless steel tube using the pulsed Ho:YAG laser (wave length: 2.1 microm, pulse duration time: 350 microseconds) and is then ejected through the metal nozzle (internal diameter: 100 microm). The Ho:YAG laser pulse energy is conveyed through optical quartz fiber (core diameter: 400 microm), while cold water (5 degrees C) is internally supplied at a rate of 40 ml/hour. The relationship between laser energy (range: 40-433 mJ/pulse), standoff distance (defined as the distance between the tip of the optical fiber and the nozzle end; range: 10-30 mm), and the velocity, shape, pressure, and average volume of the ejected jet were analyzed by means of high-speed camera, PVDF needle hydrophone, and digital scale. The quality of the dissection plane, the preservation of blood vessels, and the penetration depth were evaluated using five fresh cadaveric rabbit ventricular walls, under neuroendoscopic vision. RESULTS: Jet velocity (7.0-19.6 m/second) and pressure (0.07-0.28 MPa) could be controlled by varying the laser energy, which determined the penetration depth in the cadaveric rabbit ventricular wall (0.07-1.30 mm/shot). The latter could be cut into desirable shapes-without thermal effects-under clear neuroendoscopic vision. The average volume of a single ejected jet could be confined to 0.42-1.52 microl/shot, and there was no accompanying generation of shock waves. Histological specimens revealed a sharp dissection plane and demonstrated that blood vessels of diameter over 100 microm could be preserved, without thermal damage. CONCLUSIONS: The present pulsed LILJ system holds promise as a safe and reliable dissection device for deployment in a rigid neuroendoscope.